The pixel intervals a band or point scale assigns to its categories.
Marks are not always drawn flush to their band — Plot insets rect and cell
marks by half a pixel, and a dot sits at the band's midpoint — so matching a
pixel to a category by equality fails. Intervals let
valueAtPixel ask which band contains a point instead.
Built once per scale. The result describes the scale alone, so every caller
reading the same chart gets the same array back rather than rebuilding it.
The pixel intervals a band or point scale assigns to its categories.
Marks are not always drawn flush to their band — Plot insets rect and cell marks by half a pixel, and a dot sits at the band's midpoint — so matching a pixel to a category by equality fails. Intervals let valueAtPixel ask which band contains a point instead.
Built once per scale. The result describes the scale alone, so every caller reading the same chart gets the same array back rather than rebuilding it.